Abstract. Atmospheric emissions from wildfires in Portugal were estimated yearly over
the period 1990–2008 using Landsat-based burnt area maps and land cover
maps, national forest inventory data, biometric models, and literature
review data. Emissions were calculated as the product of area burnt, biomass
loading per unit area, combustion factor, and emission factor, using land
cover specific values for all variables. Uncertainty associated with each
input variable was quantified with a probability density function or a
standard deviation value. Uncertainty and sensitivity analysis of estimates
were performed with Monte Carlo and variance decomposition techniques. Area
burnt varied almost 50-fold during the study period, from about 9000 ha in
2008 to 440 000 ha in 2003. Emissions reach maximum and minimum in the same
years, with carbon dioxide equivalent (CO2eq.) values of 159 and
5655 Gg for 2008 and 2003, respectively. Emission factors, and the combustion
factor for shrubs were identified as the variables with higher impact on
model output variance. There is a very strong correlation between area burnt
and emissions, allowing for good emissions estimates once area burnt is
quantified. Pyrogenic emissions were compared against those from various
economy sectors and found to represent 1% to 9% of the total.